MiniDSP Flex HTx

[thcdru2k]

With your amps measuring that clean, Dirac might not add much.

 

[EJ3]

With your amps measuring that clean, Dirac might not add much.

I think that it will give me much more control in the BASS area, as these are homebuilt subs and I do not have all the cool features of newer active subs.
So it is mostly about having modern controls.

 

[thcdru2k]

Had some time to work with the Flex HTx, so here is the setup. The system is a Denon X3700H in pre pro mode (5.0, all speakers set to Large, LFE disabled) feeding a miniDSP Flex HTx with 8 by 8 analog out. Output channels feed a Monolith 2 for the left and right mains, an Adcom 7605 for the center and surrounds, Canton Karat 300 for left and right, and two HSU VTF 15H subs, the left being a Mk1 and the right a Mk2. The Karats have putty sealing the baffle edges and felt strips around the tweeters. Both subs were set to max Q, EQ2, one port open, with the volume knobs at about nine o clock.

With the AVR operating in 5.0 and no LFE channel active, LFE content is folded into the front left and right preouts. The Flex HTx receives full range left and right inputs. The left sub is fed from the left channel and the right sub is fed from the right channel. All crossover filtering is done in the Flex HTx. The Karat 300 speakers are high passed at 60 hertz using LR24 slopes and the subs are low passed at 60 hertz using LR24 slopes. No bass management is active in the Denon.

Gain matching, delay alignment, and sub to main integration were done in the Flex HTx. Denon trims are set to 0 dB and Audyssey is disabled. For these distortion sweeps, Denon master volume was set to minus 25 dB and the miniDSP output trims were at 0 dB. Based on the fundamental level in the graphs, sweep level at the listening position was in the low 80 dB range.

Measurements were taken at the main listening position with a UMIK 2 pointed straight up at 90 degrees. Just wanted to capture sound in all directions. This is an open concept room with no acoustic treatment, so reflections above about one kilohertz will influence the results.

The two attached plots show distortion for the left Karat 300 with both subs operating and the right Karat 300 with both subs operating. The graphs include the fundamental, the third harmonic, and total harmonic distortion for easy reading.

 

[Mort]

The two attached plots show distortion for the left Karat 300 with both subs operating and the right Karat 300 with both subs operating. The graphs include the fundamental, the third harmonic, and total harmonic distortion for easy reading.

How does it sound? Those fr graphs look a little rough to my eye.

I dropped the Denon x4800h and just use the htx as an AV pre-amp.

 

[thcdru2k]

How does it sound? Those fr graphs look a little rough to my eye.

I dropped the Denon x4800h and just use the htx as an AV pre-amp.

Honestly it sounds good in the room. My wife found out what I spent and didn’t even blink. She actually sat down and went through a bunch of songs and enjoyed it, and she usually has a better ear than I do, so I use her as a sanity check when I’m dialing things in. She gave me a hard time for most of the system while I was building it, but this time she didn’t.

It was a bit much for her during Stranger Things season 2, so I made a preset with a lighter low end. Between the routing, delays, and control I get out of the Flex HTx, I honestly feel like that upgrade changed more about the sound than moving up to 15 inch subs did.

 

[Mort]

Honestly it sounds good in the room.

Oh excellent.

So no DSP yet? Audyssey is good. I like Dirac better but only by a small amount. That will get it even better sounding.

 

[thcdru2k]

Oh excellent.

So no DSP yet? Audyssey is good. I like Dirac better but only by a small amount. That will get it even better sounding.

Honestly when I have some time I’m probably going to sweep each speaker individually and do a bit of manual EQ. I do want to tighten the timing and integration of everything together.

 

[Mort]

Yes. $30 for the REW integration is worth it if still in your budget.

 

[thcdru2k]

Yes. $30 for the REW integration is worth it if still in your budget.

Oh wow. I think you will saved future me ALOT of time. Thank you so much. I initially purchased a DDRC 24 but realized after I ordered that was just a 2x4 HD in disguise so I upgraded to Flex HTx through customer support e-mail so my purchased never properly got registered. I am emailing them to tie my serial number so I can purchase the integration.

 

[rirelien]

With the AVR operating in 5.0 and no LFE channel active, LFE content is folded into the front left and right preouts.

Does this mean you've set the AVR to have only 5.0 and mix the LFE in? Not sure why you'd do this, since LFE is definitionally mono -- why not use 5.1 on the AVR and then manage the LFE mix on the HTx?

(Just curious! If you're happy with the results I guess this is working for you.)

 

[thcdru2k]

Does this mean you've set the AVR to have only 5.0 and mix the LFE in? Not sure why you'd do this, since LFE is definitionally mono -- why not use 5.1 on the AVR and then manage the LFE mix on the HTx?

(Just curious! If you're happy with the results I guess this is working for you.)

AutoEQ is a solid feature. Most of its suggestions centered around the crossover region, which wasn’t where I wanted changes, so I went back to what I’m more comfortable with: manual sweeps. I only made a couple mild voicing tweaks on the right side to better match the left.

Running 5.0 is also intentional. I prefer to let the Flex HTx handle all bass management, timing, and routing on its own. It keeps the signal path clean and avoids having both the AVR and DSP trying to manage the low end. And in my head, if I’m paying for the Flex HTx, I’d rather have it set the crossover and filters than the Denon. I also tried looking into how the Denon actually manages the crossover between the subs and mains and couldn’t find anything documented, so I figured it was better to take that out of the equation. I guess I tune first for music and just let the cards fall the way they do for movies.

Here’s the 2D spectrogram of both mains + both subs:

 

[rirelien]

But the use of the word "LFE" implies source content that already has a .1 LFE channel. This is what I would do if I was keeping the AVR (which I would not, but that's just me!)

- Set L/C/R/Ls/Rs etc to "full range" on the AVR so it doesn't do bass management.
- For content with .1 LFE channel already: get that into the HTx on a dedicated input, and then you can decide what to do with that in terms of your routing/sub setup/any other filtering/delays etc.
- For the full-range signal for the rest of the channels, you can use the bass management in the HTx to route to your subs or not, as you wish.

This way, you preserve the "rumble" or sub-bass in the LFE channel in a dedicated unmixed input.

This is cleaner than your AVR mixing the LFE into the 5.0 and then you splitting it out again.

In other words: bass management is not the same as the dedicated LFE channel in x.1 content.

All just my opinions, I offer for your consideration or dismissal.

 

[thcdru2k]

But the use of the word "LFE" implies source content that already has a .1 LFE channel. This is what I would do if I was keeping the AVR (which I would not, but that's just me!)

- Set L/C/R/Ls/Rs etc to "full range" on the AVR so it doesn't do bass management.
- For content with .1 LFE channel already: get that into the HTx on a dedicated input, and then you can decide what to do with that in terms of your routing/sub setup/any other filtering/delays etc.
- For the full-range signal for the rest of the channels, you can use the bass management in the HTx to route to your subs or not, as you wish.

This way, you preserve the "rumble" or sub-bass in the LFE channel in a dedicated unmixed input.

This is cleaner than your AVR mixing the LFE into the 5.0 and then you splitting it out again.

In other words: bass management is not the same as the dedicated LFE channel in x.1 content.

All just my opinions, I offer for your consideration or dismissal.

Yeah, the big upside to your approach is having a true discrete LFE channel, which definitely gives you more flexibility if you want to shape the 0.1 track separately for movies.

For my setup though, 5.0 has just been easier to live with. I don’t even use the built in bass management block on the Flex. All my crossovers and PEQ are done on the output channels, so the Flex ends up handling the entire low end exactly the way I want it. Once you go with a discrete LFE path, you are managing two different low frequency paths and you have to keep the LFE level matched to Dolby’s spec, which I think is supposed to be about +10 dB. None of that is difficult, it is just more moving parts than I need.

So I stuck with 5.0 since it keeps my workflow clean and predictable.

 

[thcdru2k]

Had more time today messed around and went in steps of .05 / .1ms delays for sub to sub and speakers to subs. Than narrowed it down a little more. Did a frequency sweep of all 5 speakers (Canton Karat 300, M&K 750C, Polk OWM3) and both subs (HSU VTF-15H MK1 and HSU VTF-15H Mk2). Main focus was just evaluating smoothness at the crossover region. My goal essentially is to have all 7 have a unified wavefront at MLP manually measured down to .01-.05ms accuracy. This is the 2d spectrogram. I really like what the Flex HTx allows you to do.

 

[Mort]

When I run Dirac Live it calibrates 5.1 channels including the LFE.

How do I then measure that with REW? The only way to get a subwoofer measurement is by adding L+R in the matrix mixer, or do I add it in the channel router?

And what's the +10db LFE thing?

 

[Matt S]

When I run Dirac Live it calibrates 5.1 channels including the LFE.

How do I then measure that with REW? The only way to get a subwoofer measurement is by adding L+R in the matrix mixer, or do I add it in the channel router?

And what's the +10db LFE thing?

LFE is recorded 10db down, so per the bass management tab in the MiniDSP manual, you need to account for this, for example by setting all other channels down 10db.

Just remember to offset than before running Dirac (you can use the output tab to do so).

It is all in the manual. Being a man, I didn't bother reading it properly so initially had Dirac boosting my bass considerably to get a sound I liked.

I am not sure what you mean regarding REW, so will let an REW expert answer for you.

Remember that you might also need to attenuate channels for any mixing you might do from 7.1 to 5.1.

 

[deercreekaudio]

When I run Dirac Live it calibrates 5.1 channels including the LFE.

How do I then measure that with REW? The only way to get a subwoofer measurement is by adding L+R in the matrix mixer, or do I add it in the channel router?

And what's the +10db LFE thing?

If you are running REW in your connected PC or Mac over USB to the HTx, you need to keep in mind that the USB interface flips the LFE and Center Channel relative to an HDMI interface. You also need to configure your PC/Mac sound output for 5.1 channels.

 

[danstahl]

LFE is recorded 10db down, so per the bass management tab in the MiniDSP manual, you need to account for this, for example by setting all other channels down 10db.

Just remember to offset than before running Dirac (you can use the output tab to do so).

It is all in the manual. Being a man, I didn't bother reading it properly so initially had Dirac boosting my bass considerably to get a sound I liked.

I am not sure what you mean regarding REW, so will let an REW expert answer for you.

Remember that you might also need to attenuate channels for any mixing you might do from 7.1 to 5.1.

Putting the other channels down 10db does eat into potential sinad. But it also reduces chance of digital clipping if combining multiple channels (eg left and left surround)

 

[Matt S]

Putting the other channels down 10db does eat into potential sinad. But it also reduces chance of digital clipping if combining multiple channels (eg left and left surround)

Are you using an HTx and if so, have you tried to work this a different way? Analogue gain on the sub?

 

[danstahl]

I own an htx and I reduce by 10db. I don't think that there is a different way to work it